<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        .div1{
            border:2px solid red;
            background-color: red;
            width: 400px;
            height:100px;
            float: right;
        }
        .div2{
            background-color: yellow;
            width: 300px;
            height: 80px;
            float:right;
            /*清除他 左边的东西，*/
            clear: both;
        }
        .div3{
            background-color: green;
            width: 200px;
            height: 40px;
            float: left;
        }
        .div4{
            float: left;
            background-color: #29666a;
            width: 500px;
            height: 100px;

        }

        .bigdiv{
            height:500px;
            width: 100%;
            background-color: #0c91e5;
        }

    </style>
</head>
<body>
<div class="div1">div1</div>
<div class="div2">div2</div>
<div class="div3">div3</div>
<div class="bigdiv">
    <div class="div4">div4</div>

    bigdiv</div>

</body>
</html>